Untreated Crop Research Articles

Combination of irradiated chitosan and microbial agent to reduce downy mildew on grapevine cv. Thompson seedless.

Globally sustainable disease management ensuring high quality in grapes is in demand as it holds significant importance as a versatile fruit for consumption, winemaking, and production of various products such as grape juice, raisin, and grape-seed oil. The present paper reports a combination of nano-biotechnology as a promising strategy for enhancing plant health and fruit productivity in grapes combining Irradiated chitosan nanoparticles and bio-control agents. The Irradiated Chitosan with Bacillus subtilis and Trichoderma viridae and pesticides were evaluated for disease management. Percent disease index, percent disease control, and percent yield enhancement in Cymoxanil 8% + Mamcozeb 64% WP @ 0.2% treatment were as 17. 24%, 67.97% and 33.91% in 150 ppm Irradiated chitosan+B. subtilis were 19.83, 63.16, 30.41 and in Trichoderma 150 ppm Irradiated chitosan were 24.58, 54.33, and 27.40, respectively as compared to untreated crop with disease severity 53.84% PDI. Thus, irradiated chitosan and Bacillus subtilis elucidated a synergistic combination for residue-free efficient phytosanitary measures, which harnessed the strength of chitosan and bio-control agents for sustainable grape productivity. These findings will also pave the way for a deeper understanding of the synergistic interaction between Irradiated nanochitosan and bio-control agents for an eco-friendly and economically viable disease management strategy. The minimum temperature and morning relative humidity (RH I) had positive significance, with correlation coefficients of 0.484 and 0.485, respectively. The evening relative humidity (RH II) had a positive highly significant positive correlation coefficient of 0.664. Chitosan merits as a multiple stress tolerance enhancing agent that will further help in mitigating climate change adaptations in grapevines reducing reliance on chemical agro-inputs.

Phosphorus Sorption Characteristics of Acidic Luvisols and Nitisols under Varying Lime Rates, and Response Validation Using Wheat

ABSTRACT This study investigated phosphorous (P) sorption characteristics under lime rates, and validated them under field conditions. Soil samples from nitisols and luvisols were taken, mixed with lime(tha−1) at[0,0], [5.25, 3.75], [10.5, 7.5] and [15.75, 11.25], respectively, and incubated for 30 days. It was equilibrated with KH2PO4 at 0, 10, 20, 30, 40, and 50 mgPL−1. The data were tested with Freundlich and Langmuir models. External P requirement (EPR) and changes in chemical properties were evaluated. The field validation on wheat involved rates of P (0, 8.2, 16.4, 24.6, 32.9, and 41.1 kg ha−1) and lime (0, 650, and 1300 kgha−1) in a randomized complete block design with three replications. Freundlich was found the best-fitted model. Freundlich coefficient (Kf) ranged from 212 to 45 mgPkg−1 (nitisols) whereas it was 112.7 to 16.29 mgPkg−1 (luvisols). EPR (kgPha−1) without and the highest lime rate were: nitisols (142.5 and 52.32 kgPha−1) and luvisols (124.84 and 25.94 kgPha−1). Liming reduced EPR by 63.3% (nitisols) and 79.3% (luvisols). Liming increased soil pH from [4.55 to 6.60 in the nitisols, and 5.33 to 6.51 in luvisols]; exchangeable acidity (cmol(+)kg−1) 3.84 to 0.01 nitisols, and 0.72–0.05 luvisols, and available P (mg/kg) 3.2–6.32 nitisol, and 2.74–8.72 luvisols. Furthermore, applying 32.9 kgPha−1 x 1300 kgha−1 lime resulted in grain yield (4345.2 kgha−1) that was 449% more than the untreated crop (791.3 kgha−1). The validation result suggested higher P than blanket P recommendation. It also justifies that excess P or lime alone cannot be a complete solution for P management and increased yield.

Effectiveness of botanical insecticides in the management of rice gall midge (Orseolia oryzae Wood Mason)

The experiment conducted to evaluate the efficacy of ten botanical insecticides against rice gall midge, carried out at Rice research farm, B.A.U, Kanke, Ranchi, Jharkhand during kharif, 2016 and kharif, 2017, showed that the crop treated with (Aza.0.03% EC) recorded the lowest incidence of silver shoot (1.76% SS) and proved superior over all the insecticides tested during both the seasons of experimentation. It was followed by rynaxypyr 20 SC (2.54% SS), dinotefuran 20 SG (2.80% SS) and neem baan (Aza.1% EC) (3.14% SS). Similar result were found with the overall pooled mean values. The untreated control plot recorded highest incidence of silver shoot (12.05%). However, all the botanical insecticides remained significantly superior over the untreated crop of rice.

ACC deaminase-producing Ensifer adhaerens KS23 enhances proximate nutrient of Pisum sativum L. cultivated in high altitude.

A phytohormone producing, N2-fixing and 1-aminocyclopropane-1-carboxylate (ACC) deaminase synthesizing bacterium Ensifer adhaerens KS23 effectively increased the yield and nutritional contents of Pisum sativum var. Arkel. The isolate KS23 showed positive ACC deaminase activity with 174.2 (nmol of α-ketobutyrate/g-1 biomass½ h-1) a 9.7-fold increase in glutathione S-transferase activity. The proximate analysis exhibited an increased yield of protein (21.45%), carbohydrate (38.90%), sulphur (29.94%) starch (27.52%), total ash (35.57%), fat content (27.5%), nitrogen (24.06%) and hydrogen (17.91%) in treated seeds of P. sativum as compared to untreated crop seeds in field trials at Srikot village, Srinagar-246,174 (Garhwal) India. The most desirable essential and non-essential amino-acids content was also enhanced simultaneously by E. adhaerens KS23 as compared to non-treated crop seeds. This study revealed the enhancement of various nutritional contents resulting in quality improvement and an increase in growth productivity of pea. This study provides an encouraging result that may benefit the marginal income of farmers belonging mainly to hilly regions who are dependent on traditional methods of farming and thus improving their economy.

Pretreatment of crop residues by ammonia fiber expansion (AFEX) alters the temporal colonization of feed in the rumen by rumen microbes.

This study examines the colonization of barley straw (BS) and corn stover (CS) by rumen bacteria and how this is impacted by ammonia fiber expansion (AFEX) pre-treatment. A total of four ruminally cannulated beef heifers were used to investigate in situ microbial colonization in a factorial design with two crop residues, pre-treated with or without AFEX. Crop residues were incubated in the rumen for 0, 2, 4, 8 and 48h and the colonizing profile was determined using 16s rRNA gene sequencing. The surface colonizing community clustered based on incubation time and pre-treatment. Fibrobacter, unclassified Bacteroidales, and unclassified Ruminococcaceae were enriched during late stages of colonization. Prevotella and unclassified Lachnospiraceae were enriched in the early stages of colonization. The microbial community colonizing BS-AFEX and CS was less diverse than the community colonizing BS and CS-AFEX. Prevotella, Coprococcus and Clostridium were enriched in both AFEX crop residues, while untreated crop residues were enriched with Methanobrevibacter. Several pathways associated with simple carbohydrate metabolism were enriched in the primary colonizing community of AFEX crop residues. This study suggests that AFEX improves the degradability of crop residues by increasing the accessibility of polysaccharides that can be metabolized by the dominant taxa responsible for primary colonization.

Furfural wastewater pretreatment of corn stalk for whole slurry anaerobic co-digestion to improve methane production

Previous studies showed that excellent anaerobic digestion performance could be achieved using acid pretreatment, whereas the development of acid pretreatment was limited by high cost of acid consumption and severe operation. The aim of this study consisted in expanding the possibilities of low-cost acid pretreatment method for anaerobic digestion. For this, the feasibility of substituting conventional acid pretreatment with furfural wastewater was verified, and the whole slurry anaerobic digestion was performed to improve the production of methane. The furfural wastewater was used to pretreat crop stalk at different ambient temperatures (20, 35, 50°C) for different time periods (0, 3, 6, 9days). Subsequently, all treated and untreated crop stalk were digested at 35°C for 25days. According to experimental data showed that the dissimilar degradability of compositions for crop stalk was due to furfural wastewater pretreatment, and the reducing sugar content, volatile fatty acid content, pH during pretreatment phase, and their initial maximum & minimum values in anaerobic digestion phase were changed, which made a significant difference in methane production. The highest total methane production of anaerobic digestion (196.68mL/g VS) was achieved by the treatment at 35°C for 6days, which was 59.28% higher than untreated crop stalk (123.48mL/g VS). On the whole, the results showed that furfural wastewater pretreatment followed by the whole slurry anaerobic co-digestion was feasible and could contribute to application value for anaerobic digestion industry while providing an effective way for the treatment of furfural wastewater.

Chemical control of branched broomrape in processing tomato using sulfonylureas in southern Italy

The present research investigated the efficacy and the selectivity of three sulfonylureas (SUs) rimsulfuron (RS), chlorsulfuron (CS) and triasulfuron (TS) for <em>Phelipanche ramosa</em> control in processing tomato. In 2014 a single dose (D) (75, 15 and 22.5 g ha–1 active ingredient – a.i.– of RS, CS and TS, respectively), split into three applications at equal rate, was delivered into the soil layer interested by the roots using two herbigation methods i) through the drip irrigation system (DH) or ii) by foliar spray followed by overhead irrigation (FH). In 2015 SUs were applied in pre-transplant at one third of D, and in post-transplant at the dose D, at onehalf and at one-fourth of D, delivered in 3 rates by drip herbigation. In both experiments RS gave the best broomrape control and the highest yield increase compared with the untreated crop and CS improved crop yield similarly to RS despite being less effective in contrasting branched broomrape, In 2014, the foliar application of TS and CS resulted in plant injuries which, more significantly with TS, caused lower numbers and fresh weight of fruits as well as a lower crop productivity increase. In the same year the drip herbigation with TS resulted in the lowest broomrape control and tomato yield increase. In 2015, the best parasite control and tomato yield performances were obtained with RS and CS when applied in pre-transplant at 25.0 and 5.0 g ha<sup>–1</sup> a.i., respectively, and in post-transplant at 75.0 and 15.0 g ha<sup>–1</sup> a.i., respectively. With TS, the pre-transplant application a.i. was the most effective among the TS treatments resulting in a yield improvement similar to RS and CS, while it was confirmed the low broomrape control when applied through drip irrigation due to its low mobility in the soil. More research is needed in order to better exploit the combination of pre- and post-transplant applications in the chemical control of <em>P. ramosa</em> of tomato under the conditions in southern Italy.

An energetics-based honeybee nectar-foraging model used to assess the potential for landscape-level pesticide exposure dilution.

Estimating the exposure of honeybees to pesticides on a landscape scale requires models of their spatial foraging behaviour. For this purpose, we developed a mechanistic, energetics-based model for a single day of nectar foraging in complex landscape mosaics. Net energetic efficiency determined resource patch choice. In one version of the model a single optimal patch was selected each hour. In another version, recruitment of foragers was simulated and several patches could be exploited simultaneously. Resource availability changed during the day due to depletion and/or intrinsic properties of the resource (anthesis). The model accounted for the impact of patch distance and size, resource depletion and replenishment, competition with other nectar foragers, and seasonal and diurnal patterns in availability of nectar-providing crops and wild flowers. From the model we derived simple rules for resource patch selection, e.g., for landscapes with mass-flowering crops only, net energetic efficiency would be proportional to the ratio of the energetic content of the nectar divided by distance to the hive. We also determined maximum distances at which resources like oilseed rape and clover were still energetically attractive. We used the model to assess the potential for pesticide exposure dilution in landscapes of different composition and complexity. Dilution means a lower concentration in nectar arriving at the hive compared to the concentration in nectar at a treated field and can result from foraging effort being diverted away from treated fields. Applying the model for all possible hive locations over a large area, distributions of dilution factors were obtained that were characterised by their 90-percentile value. For an area for which detailed spatial data on crops and off-field semi-natural habitats were available, we tested three landscape management scenarios that were expected to lead to exposure dilution: providing alternative resources than the target crop (oilseed rape) in the form of (i) other untreated crop fields, (ii) flower strips of different widths at field edges (off-crop in-field resources), and (iii) resources on off-field (semi-natural) habitats. For both model versions, significant dilution occurred only when alternative resource patches were equal or more attractive than oilseed rape, nearby and numerous and only in case of flower strips and off-field habitats. On an area-base, flower strips were more than one order of magnitude more effective than off-field habitats, the main reason being that flower strips had an optimal location. The two model versions differed in the predicted number of resource patches exploited over the day, but mainly in landscapes with numerous small resource patches. In landscapes consisting of few large resource patches (crop fields) both versions predicted the use of a small number of patches.

The effect of biochar and crop straws on heavy metal bioavailability and plant accumulation in a Cd and Pb polluted soil

Biochar derived from various materials has been investigated with regard to its ability to decrease the bioavailability of heavy metals in contaminated soils, and thus reduce their potential to enter the food chain. However, little attention has been given to the adsorption capacity of untreated crop straws, which are commonly used as a biochar feedstock, especially in soils. Hence, this study was conducted to investigate the effect of crop straws on heavy metal immobilization and subsequent heavy metal uptake by maize and ryegrass in a soil artificially polluted by Cd and Pb. Bamboo biochar, rice straw, and wheat straw were mixed into soil four weeks before the experiment, enabling them to reach equilibrium at 2% (w/w), 1% (w/w), and 1% (w/w), respectively. The results showed that soil pH for both species was significantly increased by all treatments, except when wheat straw was used for ryegrass cultivation. Soil organic carbon was only improved in the rice straw treatment and the soil alkali-hydrolyzable N content was significantly decreased with all of the amendments, which may have contributed to the lack of an effect on plant biomass. Soil available Cd was significantly lower in the rice straw treatment than in the control soil, while Pb levels clearly decreased in wheat straw treatment. The Cd concentration in shoots of maize was reduced by 50.9%, 69.5%, and 66.9% with biochar, rice straw, and wheat straw, respectively. In addition, shoot Cd accumulation was decreased by 47.3%, 67.1%, and 66.4%, respectively. Shoot Pb concentration and accumulation were only reduced with the rice straw treatment for both species. However, metal uptake in plant roots was more complex, with increased metal concentrations also detected. Overall, the direct application of crop straw could be considered a feasible way to immobilize selected metals in soil, once the long-term effects are confirmed.

Estimation of avoidable yield loss inGerbera jamesoniicaused byMeloidogyne incognitaunder greenhouse conditions

Yield loss caused by root knot nematode in gerbera (Gerberajamesonii Hook) was assessed as 30.21 to 36.90 per cent, respectively in experiments run twice simultaneously with different varieties, viz. Alabanda Red and Palm Beach Yellow. Significant reduction in shoot length, root length and shoot weight were observed due to root knot nematode infestation. Regarding the flower yield, infestation due to M. incognita in gerbera variety Alabanda Red and Palm Beach Yellow significantly decreased the floweryield 134 and 106No m−2 recorded in untreated crop as against 192 and 168 No m−2, respectively in carbofuran treated crop. The nematode also deteriorates the quality parameters of gerbera, viz. stalk length and flower diameter.

Identifying traits leading to tolerance of wheat to Septoria tritici blotch

Identifying tolerance traits to diseases in wheat genotypes has an increased interest to minimize pesticide use and to complement resistance and escape.Yield tolerance to Septoria tritici blotch (STB) was studied pooling up three experiments involving 18 genotypes, 5 years and 6 sites in France, amounting to 161 genotype×year×site×management combinations. Each combination involves a crop pair (treated or not against foliar diseases) repeated two to three times. Most crops were grown under high fertilization, and STB was the main disease present in untreated crops. Crop traits (ear density, grain number and weight, area of leaf laminas) were recorded; green area of leaf laminas over time was fitted to a Gompertz equation, producing metrics for senescence traits (time and duration).Over the whole dataset, LAI from 1.1 to 7.5m2m−2; yields from 280 to 1122gDMm−2 and relative yield losses up to 70% were recorded. Fungicide treated crops exhibited slightly larger ear density and leaf lamina area independently of the intensity of epidemics. As an overall trend, yield became more determined by source traits when epidemics occurred. Yield loss was proportional (r2=0.7) to senescence advance by disease. Decrease in grain number and weight were also correlated (r2=0.4 and 0.8, respectively) to yield loss. Two epidemic indices were built to compare data across year×site combinations. Then yield in untreated crop was predicted (r2=0.87) from yield in corresponding treated crop, and interaction of epidemic indices with traits of the treated crops that therefore were pointed out as responsible for tolerance variability. Late senescing crops exhibited a greater tolerance to epidemics. Conversely, grain weight was a major key of intolerance. To minimize the trade-off between yield potential and tolerance it is thus suggested to maximize grain number.This study represents a first step in identifying key traits involved in tolerance to STB in varying agronomic conditions and cultivars.

Management of stable fly and other nuisance flies breeding in rotting vegetable matter associated with horticultural crop production

Stable-fly (Stomoxys calcitrans L., Diptera: Muscidae) and other nuisance flies breeding in horticultural substrates around the Perth metropolitan area of Western Australia were investigated with regard to their larval habitats and relative abundances. Substrates were found to comprise either crop residue (i.e. stalks, leaves and fruit) left in or on the ground after harvesting, or harvested crop waste (i.e. reject produce or processing scraps dumped into open pits or fed to livestock). Stable-flies were the predominant species (>85%) developing from a wide variety of trashed vegetable crop residues. Other flies developing from these materials included house-fly, lesser house-fly, false stable-fly, blue-bodied blow-fly, black carrion-fly and flesh-flies. Stable-fly development was reduced by >90% when crop residues were sprayed with diazinon or chlorpyrifos, either prior to or immediately after incorporation of the residue into soil. Untreated crop residues yielded several hundred to >1,000 stable flies/m2 of production. Insecticides applied several weeks after crop residue incorporation into soil did not significantly reduce stable-fly emergence.

Effects of Zinc fertilizer application on the incidence of rice stem borers (Scirpophaga species) (Lepidoptera: Pyralidae) in rice (Oryza sativa L.) crop

Use of fertilizer within plant protection system can prove a key factor for pest management strategy. The effects of Zinc sulfate (33% - Zn) fertilizer on the incidence of rice stem borers (Scirpophaga species) (Lepidoptera: Pyralidae) in rice crop were investigated. The Zn was applied using broadcast method at three levels (20, 25 and 30 kg/ha) in the vicinity of the roots, 30 days after crop transplantation. The results of field experiment on rice cultivars Shadab and Mehak showed that Zn had significant influences on the stem borers population and paddy yield over the unfertilized control. Average yield per hectare was increased at all doses of Zn and by applying it at the rates of 20, 25 and 30 kg/ha, the differences in grain yield were not significant, but production increased significantly over the untreated crop due to varying pest prevalence. With respect to borers incidence, higher dose 30 kg Zn/ha markedly decreased infestation, while, applications at 20 and 25 kg permitted slightly more deadhearts and whiteheads incidence, but differed significantly from unfertilized control. The present study implies that due to suppressive effects of Zn fertilizer on the incidence of the rice stem borers at crop maturity stage increased grain yield, and the use of soil amendments strategy can create an unfavorable environment for pest inducing resistance through anti biosis or feeding inhibition. Key words: Rice, Oryza sativa, Scirpophaga, insect control, rice stem borer, Zinc.

Risk of salmonellosis from consumption of almonds in the North American market

Salmonellosis outbreaks from consumption of raw almonds in 2001 and 2004 led to regulations that require mandatory treatment of almonds sold in North America to give a minimum 4-log reduction of Salmonella. This study aims to: 1) assess the risk of salmonellosis associated with almond consumption in North America, with current treatments in effect; 2) determine the resilience of the current production system to increases in prevalence or concentration of Salmonella on almonds; 3) assess the impact of treating less than 100% of the crop; and 4) investigate conditions that could explain the number of cases associated with the 2001 outbreak. Risk was assessed using a Monte Carlo simulation, based on an established dose–response relationship. Data for almond amounts sold, Salmonella prevalence and concentration on almonds, storage time and temperature at different handling steps, population reductions during storage at various temperatures and with different treatments, and consumer handling were based on data from published sources and almond industry or academic expert opinion. What-if scenarios were evaluated for Salmonella prevalence varying from 1 to 65%, concentrations of Salmonella varying from 1 to 120MPN/100g, and portions of untreated crop varying from 0 to 10%. The estimated incidence of salmonellosis in North America from almonds as currently treated is on average 0.008 cases per billion servings (with an estimated 6.6billion servings consumed annually). Increases in Salmonella prevalence to 25%, mean concentrations above 25MPN/100g, or leaving 0.05% of the crop untreated all resulted in an arithmetic mean risk greater than 1case/year (with geometric means remaining below 1case/year for all variables). Assuming 4000kg at a prevalence of 65% (observed in recalled lots) and an average concentration of 120MPN/100g in raw almonds (back calculated from levels in recalled almonds) predicted over the 2800 cases estimated for the 2001 outbreak. Applying a 4-log reduction to these almonds reduced the average number of predicted cases to less than a single case. The current regulation is effective in maintaining the risk of salmonellosis from consumption of almonds below an arithmetic mean of 1case/year, although significant increases in either prevalence or concentration, or small increases in proportion of untreated almonds would frequently lead to exceeding this threshold.

Integrated Nutrient Management by Using Target Yield Equations for Rice-Jute System in Eastern India

ABSTRACT Field studies on target yield equation (TYE)-based integrated nutrient management in rice (Oryza sativa) and jute (Corchorus capsularis) were conducted to investigate its value in achieving target yields, improving nutrient utilization and soil nutrient status. The study was conducted for 3 years consecutively during 2001 to 2003 under on‐farm rainfed conditions growing rice variety Padmini in sequence with jute variety JRO 524 during wet season (April to December). Requirement of nitrogen (N) phosphorus (P), and potassium (K) for achieving target yield of 4 t ha−1 for rice and 3 t ha−1 for jute was estimated following a soil test crop response (STCR)-based TYE. Four sets of treatments included farmyard manure (FYM) as organic source and synthetic fertilizers as chemical source applied to both rice and jute, compared with an untreated crop (no NPK) usually followed in farmers' practice. Results showed marginal deviation from specified target yield, achieving 96% of the target yield in rice and 95% in jute. Integrated nutrient management resulted in significantly higher yield of both rice (3.84 t ha−1) and jute (2.85 t ha−1), treated with 100% INM combined with 75% fertilizer NPK + 25% organic N. As a result, the system productivity aggregating rice and rice equivalent yield of jute was also highest (8.97 t ha−1) with 100% INM. A benefit:cost ratio was also derived, showing a maximum of 1.04 in rice with 100% INM, compared with 0.96 with the application of fertilizer alone. Nutrient uptake and nutrient productivity were also higher in crops with 100% INM. In addition, sustained availability of soil N, P, and K (and thereby, improvement in soil nutrient balance), was pronounced more with 100% INM. Therefore, the 3-year on-farm study showed that TYE-based INM not only helped achieve near-target yields but also promoted nutrient utilization and sustainable soil NPK status.

Effect of crop residue management on nitrogen dynamics and balance in a lowland rice cropping system

Two field experiments were conducted in a rice–fallow–rice cropping sequence during consecutive dry and wet seasons of 1997 on a Fluvic Tropaquept to determine the fate and efficiency of broadcast urea in combination with three residue management practices (no residue, burned residue and untreated rice crop residue). Ammonia volatilization losses from urea (70 kg N ha−1) broadcast into floodwater shortly after transplanting for 11 d were 7, 12 and 8% of the applied N from no residue, burned residue and residue treated plots, respectively. During that time, the cumulative percent of N2 + N2O emission due to urea addition corresponded to 10, 4.3 and nil, respectively. The 15N balance study showed that at maturity of the dry season crop, fertilizer N recovery by the grain was low, only 9 to 11% of the N applied. Fifty to 53% of the applied 15N remained in the soil after rice harvest, mainly in the upper 0–5 cm layer. The unaccounted for 15N ranged from 27 to 33% of the applied N and was unaffected by residue treatments. Only 4 to 5% of the initial 15N-labeled urea applied to the dry season rice crop was taken up by the succeeding rice crop, to which no additional N fertilizer was applied. Grain yield and N uptake were significantly increased (P=0.05) by N application in the dry season, but not significantly affected by residue treatments in either season.

Evaluating the effectiveness of a hydrophobic polymer for conserving water and reducing weed infection in a sandy loam soil

In this work we tested the influence of different solutions of a hydrophobic polymer named Guilspare ®, applied to the soil surface to reduce soil evaporation, on the soil water status, soil temperature, crop performance and weed emergence. Two tests were carried out on a farm of the Guadalquivir river valley, southwest Spain, one with a maize crop and the other with bare soil. In the test with maize, we evaluated the effect of applying a solution of 2% v/v of Guilspare ® in water, at the rate of 3 l m −2, on the crop performance and weed emergence. On both the treated and the untreated control plots, three rates of irrigation were applied, namely 100, 75 and 50% of the locally determined optimal irrigation depth to cover the crop needs for an optimum development and yield. For the case of 50% of the irrigation dose, the performance of the crop treated with the polymer (T50) was much better than that of the untreated control plot (C50). The crop height and green leaf area index for T50 were nearly as good as for the C100 control plants receiving 100% of the irrigation dose. The T50 crop was 73% of the yield of the treated and fully irrigated T100 crop, while the C50 yield was only 38% of the C100 yield. The treated crop reached the different phenological stages quicker than the untreated crop. The polymer was effective in reducing weed emergence. In the test with bare soil, 0.8% v/v of Guilspare ® in water, at the rate of 1 l m −2, kept levels of water content in the soil as high as other solutions with greater amounts both of polymer and water. The average soil water content during the irrigation period in this lower treatment was 34 and 53% higher at depths of 0.15 and 0.25 m, respectively, than in the untreated plots. No influence of the polymer on soil temperature was observed. Results from additional measurements on weed emergence and hydraulic conductivity of the soil surface showed that the polymer was still effective 7 months after application. In fact, the hydraulic conductivity in the range near saturation was 44% greater in the treated plots than in the untreated ones, and the number of weeds was 27% lower.

Predictors of blood lead levels in agricultural villages practicing wastewater irrigation in Central Mexico.

To investigate whether the agricultural use of untreated wastewater (i.e. crop irrigation) was associated with elevated blood lead levels in a farming population in the Mezquital Valley and which risk factors, other than exposure to untreated wastewater, were associated with elevated blood lead levels, lead levels were measured in venous blood obtained from 735 individuals. Blood samples were analyzed by atomic absorption spectrophotometry. Food habits and dietary intake were gathered by interview, using a semi-quantitative food-frequency questionnaire. The average blood lead level was 7.8 microg/dL (SD 4.66 microg/dL; range 1.2-36.7 microg/dL). 23% of the study population had blood lead levels exceeding 10 microg/dL. The use of lead-glazed ceramics (LGC) was significantly associated with elevated lead levels (p = < 0.001). Other significant variables included age, gender (males), and non-farming-related occupations (e.g., technicians, factory workers). p = 0.005, 0.08, and 0.001, respectively. When the analysis was stratified by the use of LGC for food preparation, an inverse relationship between higher daily calcium intake and blood lead level was detected (beta = - 0.040, p = < 0.05). Thus, blood lead levels were positively associated with the use of LGC. Calcium intake showed a protective effect, maybe by decreasing absorption of lead in the gastrointestinal tract. No association between occupational exposure to untreated wastewater or crop consumption and blood lead levels was detected. Further environmental and health surveillance is recommended.

The Effect of In-Silo Effluent Absorbents on Effluent Production and Silage Quality

Experimental data on the effects of absorbent inclusion in the silo on effluent production and silage quality is reviewed. The absorbent materials used in various studies include straw, hay, paper, bentonite, polymers, cereals, dried sugarbeet pulp, various by-products and compound feeds formulated to reduce effluent and enhance silage quality. Most studies have shown absorbent inclusion (20–80 kg/t) to reduce total effluent production by 20–85%. The amount of effluent retained per unit of absorbent varied widely for different absorbents and for the same absorbent in different experiments. This variation cannot be attributed simply to differences in experimental procedures and implies that crop characteristics such as proportion of stem, amount of surface water, etc. influence the effectiveness of absorbents. Highly lignified materials (hay, straw, newspaper) and absorptive minerals (bentonite), though highly absorptive, adversely affect nutritive quality and are unlikely to find application in current conservation systems. The inclusion of cereals in the silo has generally improved fermentation and nutritive quality but their effectiveness as absorbents is questioned in several experiments. Inclusion of dried sugarbeet pulp has almost invariably reduced effluent production although the amount retained has varied widely between experiments. Sugarbeet inclusion improved fermentation and reduced losses when the untreated grass was poorly fermented. Silage quality was improved by sugarbeet inclusion; the overall efficiency of inclusion, compared to supplementary feeding, appears to depend on the extent to which sugarbeet inclusion influences in-silo losses and silage intake. The results repeated for proprietary absorbents have been generally similar to those for sugarbeet. The evidence available suggests that incorporation of sugarbeet or proprietary absorbents in the silo would be beneficial, particularly if the untreated crop is likely to be poorly fermented. The main factors mitigating against these or other absorbents is the unpredictability of effluent retention and the additional labour, resources and silo space required at harvest time.

Comparison of aerobically-treated and untreated crop residue as a source of recycled nutrients in a recirculating hydroponic system

This study compared the growth of potato plants on nutrients recycled from inedible potato biomass. Plants were grown for 105 days in recirculating, thin-film hydroponic systems containing four separate nutrient solution treatments: 1) modified half-strength Hoagland's (control), 2) liquid effluent from a bioreactor containing inedible potato biomass, 3) filtered (0.2 μm) effluent, and 4) the water soluble fraction of inedible potato biomass (leachate). Approximately 50% of the total nutrient requirement in treatments 2–4 were provided (recycled) from the potato biomass. Leachate had an inhibitory effect on leaf conductance, photosynthetic rate, and growth (50% reduction in plant height and 60% reduction in tuber yield). Plants grown on bioreactor effluent (filtered or unfiltered) were similar to the control plants. These results indicated that rapidly degraded, water soluble organic material contained in the inedible biomass, i.e., material in leachate, brought about phytotoxicity in the hydroponic culture of potato. Recalcitrant, water soluble organic material accumulated in all nutrient recycling treatments (650% increase after 105 days), but no increase in rhizosphere microbial numbers was observed.